Cliff, I rebuilt one a few years back for an MC8 I had briefly. Ordinary tools will be all you need. If you don't have an exploded diagram to work from, take lots of digital pics as you go, since there's a lot too 'em. I'd also recommend digging into the whole can and taking each part out prior to ordering parts. You might find springs and such that need to be replaced. Some of the ball bearings might be too flat, etc. Order new breathers and cotter pins, too. You might consider replacing the service side diaphram while you're at it. That way you'll never have to touch the can again. Plan at least 4 hours for the job and don't feel rushed.

For the rebuild, I got my parts from Mohawk Manuf. and they were awesome to work with. Since I was in a hurry, they overnighted the parts to me for only FedEx rates (no "rush" charges). Luke is great, also. I spent about $120 or so a lot of the guts. On mine the can had been exposed to water and road salts and had major rust/ corrosion.

Do you have a parts manual? I did for the MCI can I was rebuilding, and made it much easier on myself and the Mohawk folks to have the proper numbers.

Cliff, I'm so glad that you broached this subject, no only because we're having a similar problem with releasing our Parking brakes but because I had a discussion with my bus mechanic, David, today about brake actuators. New DD-3's are going for over $500 bucks now and David feels that instead of replacing mine with DD-3"s I should replace them with the 30-30's which the trucks use...for the reason that once you push the button to dis-engage the parking brake...it goes off...you don't have to do the Potomac Two Step on the pedal to get them to release.

Initially I thought he was talking about the spring brake actuators but from what I was led to believe the 30-30's are smaller than the spring brake actuators and can be bought re-built for around $80 ea, exchange.

Now we're going to have to be patient and hear from our experts on the subject.

Also, Uncle Ned and I have asked David if he and his wife, Roxie, would join us at Dallas' bash in October. We're happy to have a man of his talent and knowledge of buses so close to us and I'm sure he would, if we could arrange it with Dallas and Cat, talk to us about buses in general and share some of his knowledge and have perhaps a Q & A session.

Bob

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Gosh, I stepped in this one.....Bob wanted an 'expert'....... info is valid, just not my credentials!

Bob, On MCI buses, Due to the way the mounting bracket is made, there's not enough room to replace the DD3 with 30/30 chambers.

« Last Edit: July 27, 2006, 05:02:52 PM by ChuckMC8 »

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Far better is it to dare mighty things,to win glorious triumphs,even though they may be checkered by failure, than to rank with those poor spirits who neither enjoy nor suffer much,because they live in the gray twilight that knows neither victory nor defeat. Theodore Roosevelt (1858-1919)

Clifff: It is a long time since I took a DD-3 apart. Get a big felt pen and mark the orientation of all the fittings and draw a line down one side of both cans so that you get everything back in the right position the first try. IIRC the clamp ring needed a 12 point socket to remove it. The spring is not as powerful as a spring brake but will still make things come apart rather quickly if you don't have some method to control it.

NCBob: Can you get some more info from your mechanic on the brake cans he proposes - make and model?

Cliff, have you checked the Bendix website? There are some pix located at this address.... http://www.bendix.com/downloads/air_brake_handbook/Control_section_3.pdfIf this doesn't load correctly, just take the link back to Bendix.com and look around. There's a troubleshooting chart on this site also. I've never had a lot of success using diag charts, but they help build a knowledge base that is useful. Here I go again .... modifying brakes systems can be problematic. This ain't directed at you Cliff...you're not modifying anything. These various brake systems have many interdependent components that may cause problems if modified...and death and dismemberment once the operator notices something doesn't work quite right. Bendix DD3s are proven brake chambers. Spring brakes and 30/30s fail too. Fix your DD3s and get on with other things....May I suggest that before any brake systems are altered, that schematics of both the existing bus system and the system that is used with (in this case brake chambers) be overlayed and compared. Compare part numbers and valves. Then an idea of the level of difficulty required to correctly change the bus brake systems will become more apparent...maybe they aren't as different as I think? If parking brakes don't release correctly, there's something wrong with the system. Fix what ails it. Just disassembling the drive axle chambers and cleaning and lubing may work wonders...or an inexpensive valve is not working. Could also be the result of years of moisture crud and corrosion buildup. DD3s are not difficult to repair...IMHO what's gonna be hard to work on is a bastardized system with no manuals or absolute replacement parts. I don't doubt that a good brake man couldn't rig something that may work...but who's going to followup later? An unknowing mechanic that knows buses may make inappropriate repairs without understanding that the system has been modified. Just sooo many ways this could go bad. Last but not least, anyone with parking brake release issues should be certain that they are following the correct release process.Alas, I doth prattle too much! But I did get the grass mowed tonight! JR

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JR Lynch , Charlotte, NC87 MC9, 6V92TA DDEC, HT748R ATEC

"Every government interference in the economy consists of giving an unearned benefit, extorted by force, to some men at the expense of others.”

Cliff, I rebuilt mine also. I would suggest you tear completly apart and replace rubber and worn parts.

NCBob, The 30-30 is a spring brake. 30 is the surface area of the brake and spring area (sq in ). You can buy 24-24, 30-30, 30-24, 36-30, 30-30 etc. The 30-30 is the most popular. I have a MCI 5C and COULD NOT fit spring brakes in. Hope this helps. Tom Y

We modified the mounts and went with spring brakes. While there are liability issues, we made a point of doing two things: we have exactly what is used on a truck tractor and we were careful to make sure that we did not develope any weaknesses in the braking system.

Cliff, I'm not sure which "Brian" you are referring to, but yes I did rebuild my cans.

However, I did not rebuild the internal locking guts of my cans because the shafts were completely worn out. I ended up getting used DD3 cans from Luke @ US Coach and then put new diaphrams in them. Let me just say putting the diaphrams in is really easy. Basically nothing to the job if you are careful and take your time. Also, it is really easiest to do the job with the tires off, but you might be able to do it with the tires still on. Just make sure to block up the coach body and chock the wheels so the bus can't move when you release the parking brakes.

I dont know where the $200 for parts comes from..the diaphrams are $64 for the pair on each side (from Mohawk). My locking components (rollers and brake shaft) were fine...so ..where is the other $140.00 ?

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Far better is it to dare mighty things,to win glorious triumphs,even though they may be checkered by failure, than to rank with those poor spirits who neither enjoy nor suffer much,because they live in the gray twilight that knows neither victory nor defeat. Theodore Roosevelt (1858-1919)